Radio program detector



April 1, 1930; K. G. KARSTEN 1,752,302

RADIO PROGRAM DETECTOR Filed Aug. 20, 1925 Rad 1:0

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ATTO RN EY Patented Apr. 1, 1930 UNITED STATES KARL G. KARSTEN, OF NEW YORK, N. Y.

RADIO PROGRAM DETECTOR Application filed August 20, 1925. Serial No. 51,351.

.This invention relates to improvements in apparatus for indicating the reception of radio oscillations at different wave-lengths, so that the operator of a radio set can in a moments time determine at what wavelengths stations are transmitting at that instant.

Desciibingthe apparatus generally, it has a switch device WhlCh permits the connection of the usual antenna of a radio set to an untuned amplifying and detecting arrange-l ment, and a plurality of indicating systems, each having a circuit connected to 'such amplifying and detecting arrangement, and tuned to a particular band of wavelengths which it may be desiredto indicate, each having a control relay actuated by currents from its particular tuning circuit, and each having an indicator governed or controlled by its respectiverelay.

One form of execution of the object of this invention isset forth on the accompanying drawings, in which the figure represents the circuit diagram for such an indicating device for five bands of wave-lengths.

Since this apparatus is intended for use in conjunction with a radio receiving apparatus, a single aperiodic antenna 10 is provided for bothdevices, with a lead-in to the blade of a vtwo point switch 11; from one point of this switch a conductor leads to the radio receivingset R, with a return by wire 12 to the ground at 13. The other point of the switch 11 is connected through a blocking condenser 14; to the grid of an amplifying tube 15. The anode of-this tube 15 is connected through the blocking condenser 1 with the grid of a second amplifying tube 17, which in turn is connected by bus wire 18 4 to the series of tuning circuits as will-be described hereinafter.

Alternating current supply mains 19 are employed as a source of current for the fila- -ments of the tubes 15 and'l'l'. A switch 20 is connected in series with these mains with a line passing through the primary of a transformer 21. A secondary of this transformer 21 is connected to, the filaments of the tubes 15 and 17-, which are shown as connected in multiple, with the stopping condensers 22 and 23 connected in shunt to the filaments, andwith the middle point between the condensers connected to the ground bus 12; this permits the use of alternating current for heating the tubes Without setting up an 55 alternating current hum-from the power line.

A resistance coupling is indicated between the various circuits across the tubes, since this has been found in practice to be well adapted for, the purpose of maintaining an untuned and unselective amplification. The grid leap resistances 24C, 25, are connected at one endof each to the grid of the respective tubes 15 and 17 and are connected together at their other terminals by a wire 26, which $5 is continued to the negative terminal of a biasing battery 27, which has its positive terminal connected to the ground bus 12.

It willcbe understood by a person skilled in the art that when the switches are thrown, to by means'of the common connection 50, to

the lower position, that the circuits are so connected that the signal oscillations of any and all frequencies within the range of the apparatus, U amplified and delivered the bus wires18, 33 in the output circuit of tube 17 A plurality of tuned circuits, each preferably having two inductances and capacities of a fixed value so that each circuit is in 80 resonanceto a narrow band of frequencies 6 different from those of the other circuits but within a selected broad band of wavelengths, are connected across the bus wires 18, 33; five of these are represented in the drawings as I, II, III, IV, V and since they are similar except for the constants of value of inductances and capacities, the descrip tion of one will suflice for all. -.With a wavelength range of from 220 to 570 meters, for '90 as received a the antenna, are J5.

example, each of the circuits is constructed latory circuit consisting of the inductance L o ing systems II, III, IV, and V is the same,

and the-condenser 0, connected in series with a resistor Z. This resistor Z is preferably constructed of a material having a high coefficient of thermal change of conductivity, such as tungsten, which for the reduction of heat losses is enclosed in an evacuated tube; a low candle power tungsten lamp bulb may be employed. This oscillatory circuit is connected across the bus wires 18, 33 through the stopping condensers 32 which serve to prevent the flow of direct current through the inductance L which is in shunt to the coupling resistance 29.

tThe resistor Z constitutes one arm of a Wheatstone bridge, which has a balancing arm including the similar resistor X, and a pair of arms constituting the potentiometer 34, with the movable contact 35 to adjust the ratio of the arms in regulating the device at first setting. Connected across the bridge in shunt to each pair of arms is a winding of a balanced relay here diagrammatically represented as a solenoid 36, mounted upon a common core with a second winding likewise represented as a second solenoid 37, which is'traversed by direct current from a battery 38, as controlled from a switch 39, and. flowing through the relay energizing bus wires 40, 41. A conductor 42 leads from'the movable contact 35 of the potentiometer to the bus wire 40, and the Wheatstone bridge is complted by the conductor 43'extending from the mm 44 connecting the two resistors Z and X to the buswire 41. The core of the solenoids 36 and 37 actuate an armature 45, when current flows through the solenoid 36, to bring it into conductive relation with the contact 46. The armature is connected to a bus wire 47,

and the contact is connected through an indicating device S shown as an electric lamp, to the bus wire 48. These bus wires47, 48 are connected to the terminals of a secondary49 in-lnductive relation with the primary of the transformer 21, so that the current for lightmg th lamp bulb S is derived from the al ternating current mains. l

The operation of'each of the other indicatand in general the respective component parts have been designated by the same letters with an appropriate superscript. The operation for each is the same, and the respective lamp S S S, S is lighted to indicate that a station is being received on the respective wave-length band.

The operation of the device may be outlined as follbws-:

In assembling and installing the device, the respective potentiometers 34 are adjusted until the resistors Z and X, do not give a response across the solenoid 36 when current from battery 38 is applied across the bridge.

WVhen the operator wishes to determine what stations are transmitting, the switches 11, 20, 39 are moved by'means of a common connection 50 into the lower position, so that theantenna 10 is connected through the untuned amplifier arrangement to the ground at 13. The signals from all stations are received and amplified and these signal 'currents are delivered to the output bus wires 18, 33.These individual oscillatory circuits I, II, III, IV, and V, being tuned to difi'erent'wave-length bands will respond to the stations transmitting, if any, within-their range. By this response, currents are set up in the oscillatory circuits which flow through resistors Z, .causing a variation in their temperature and a corresponding change in resistance. This change in resistance of Z unbalances the bridge and current will then flow from bat tery 38 through the bus wires 40, 41 and the switch 39, to the movable contact 35 of the potentiometer, thence through the respective halves of the potentiometer winding 34 and thus producing a drop of potential across the potentiometer which incites a current through the solenoid 36. This causes the magnetization of the relays 36, 37, 35 to produce the closure of the armature 45 upon its'contact 46, and permits current to flow from the secondary 49 of transformer 21 bybus w re 47 to the armature 45, thence to itscontact 46,

through the indicating lamp S, to bus wire 48 and back to the secondary 49. The lamp is then lighted, and indicates that a station 1s transmitting somewhere Within the wavelength band for which the circuit I is adjusted.

A similar action occurs for any other of the oscillatory circuits, II, III, IV or V, if waves are received at the antenna from stations transmitting within their bands. If a particular lamp lights, the indication denotes that a station is transmitting within the'range; and vice versa, if a lamp is dark, no station is indicate If for example, the signal lamps, S, S? and S are lighted while the signal lamps S and S remain dark, the operator will understand of action.

for the indicator lamps themselves is. interrupted by the switch blade 20. In this way,

the entire indicating apparatus is thrown out On the other hand, the switch blade 11 disconnects the indicating apparatus on its input side, and connects the antenna 10 to the radio receiving set R, which may then be tuned in the ordinary manner and responds to a station within the wave band III; of course, the operator moves within a relatively short range of frequency the settingof the dials of this radio set R, which must be established to receive the station or one of the stations which has caused the brightening of the signal or indicating lamp S.

If it is desired to listen to a station in the bands of groups I or V, a similar manipulation of the switches occurs, and the radio set R is tuned within the respective ranges.

It is apparent that many changesmay be made in theform of execution of the invention without departing from the scope of the appended claims.

Having thus described my invention, what I claim is":

1. In anindicating. device for high frequency currents, an oscillatory circuit tuned to such frequency currents, a device in series in such oscillatory circuit whose resistance varies with the passage of current therethrough, a balancing device and a potentiometer having an intermediate tap, conductor means connecting said devices and potentiometer in a-closed series with one another, a source of direct current connected to the intermediate tap of said potentiometer and to the conductor between said devices, an output solenoid connected in shunt of said potentiometer and indicating means controlled by said solenoid.

2. In an indicating device for quency currents, a tuned oscillatory circuit, means to connect said oscillatory circuit to a source of high frequency current at times emitting signals of its own tuned frequency, a device in said oscillatory circuit responsive to thepassage of currents of such frequency through said oscillatory circuit, a relay having anenergizing and an indicating winding, means to energize said energizing winding, means controlled by said device to energize said indicating winding, and an indicating means connected with said relay whereby the passage of such a signal current through said responsive device will cause a change in energization of said relay and produce an operation of said indicating means.

3. In a device for indicating the reception of signals from stations of different frequency, an antenna circuit, a common amplifier and a plurality of tunable oscillatory "circuits supplied thereby and individually tuned to separate frequency hands, a respective current responsive resistor 1n each of said oscillatory circu ts, a balancmg resistor high frein each said circuit, a potentiometer in each said circuit, conductor means to connect said resistors and potentiometers respectively in closed series to form Wheatstone bridges of which each arm comprises a resistor and part of the respective potentiometer, a respective relay including a solenoid connected in shunt of each said potentiometer, indicating means controlled by said relay, and means to supply current across the pairs of bridge arms, whereby change of the current through said respective current responsive resistor will produce a change of energization of said relay and indicate the passage of current through the respective oscillatory'circuit.

4. In a device for indicating the reception of signals from stations of different frequency, an antenna circuit, an output circuit, an untuned amplifier to receive signals from said antenna circuit and deliver them to said output circuit, a plurality of tuned oscillatory circuits each covering a predetermined portion of the total frequency reception range, and connected across said output circuit, a resistor in series in each of said oscillatory circuits and adapted to be-changed in resistance by a current flowing in said oscillatory circuit, and a plurality of indicating means connected to the resistors whereby each indicating means is operated by the change of resistance in its respective resistor.

5. In an indicating device fo-rhigh frequency currents, a tuned oscillatory circuit, means to connect said oscillatory circuit to a source of high frequency current, a device in said oscillatory circuit responsive to the passage of currents therein 'of its tuned frequency, a balancing device and a potentiometer connected in series with said device to form a bridge having arms each comprising one of said devices and a portion of the potentiometer, means to supply direct current to the arms of the bridge, a relay having an energizingand an indicating Winding, said indicating winding being connected in shunt across said bridge, said energizing winding being supplied with direct current from the aforesaid means, a source of alternating current, an indicating device, and a circuit including the armature of the relay and its contact, said source of alternating current and said indicating device.

6. In an indicating device for high frequency currents, an untuned or aperiodic amplifying device for said currents, and a plurality of individually tuned detector and indicator devices connected in multiple to the output of said amplifyingdevice, each of said detecting and indicating devices including a tuned oscillatory circuit to select from such currents thoseof a given periodicity band, a resistor thermally responsive by change of resistance to the passage of current therethrough whereby to detect the passage of such currents, a resistor of similar temperature characteristics, fixed resistances connected to said resistors whereby to form a balanced bridge, means to impose a uni-directional current on the arms of said bridge, and an indicating device connected to the mid-points of said arms. I

7. In an indicating device for high frequency currents, a bridge comprising two shunt conductors each'containing a fixed resistance anda resistor, said conductors being balanced with respect to each other and said reslstances each having one terminal connected by portionsvof said conductors to a- I terminal of the other, one of said resistors being thermally res onsive by change of resistance to a high requency current, means to impose a uni-directional current upon both conductors in shunt of each other, indieating means responsive to difierences of resistance in said conductors and connected to each conductor at a responsive point intermediate the respective resistance and resistor, and means to impose a high frequency current on said thermally responsive resistor.

8. In an indicating device for high frequency currents, a bridge comprising two shunt conductors each containing a resistance and a resistor, said resistors being adapted to change in resistance in response'to change of temperature thereof, said resistances each having one terminal connected by portions of said conductors to a terminal of the other, I said conductors being balanced by said resistors with respect to each other so that changes of atmospheric temperature are with-.

out effect upon the bridge, means to impose a uni-directional current upon both conductors in shunt ofeach other, means to impose a high frequency current on one of said thermally responsive resistors whereby to change its temperature and resistance, and an indicating means including a current operated device connected to each of said conductors intermediate the responsive resistance and resistor and responsive to the flow of current produced by the differences of potential at such points resulting from the change of resistance of said one of said resistors.

9. In an indicating device for high frequency currents, a. bridge comprising two shunt conductors each containing a fixed resistance and a resistor, said conductors being balancedwith respect to each other and said resistances each having one terminal connected by portions ofsaid conductors to a terminal of the other, one of, said resistors being thermally responsive by change of resistance to a high frequency current, means to impose a uni-directional current upon both conductors in shunt of each other, means to impose a hlgh frequency current on said ther- 'mal1y responsive resistor, a relay having an .exciting coil, indicating means controlled by v sald'relay, and arelay conductor including said coil and connectedto each of said con- 

